PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Merrell Mimosa Emme White Gray Leather Mary Jane Sport Trail Hiking Flats 8.5 , Womens Ladies Slip On Loafers Diamnate Casual Fashion Pumps Mocassins Shoes SizeSUPER Brown Felt/Wool HAFLINGER "FRILL" Ballet Flats 40 , Antonio Melani Womens Gigi Black Suede Loafers Shoes Moccasin Flats Size 8M NWOBLacoste Womens Loafers Marice Slip On Size 9 Shoes WhiteSoft Spots supremes vertex women shoes 11 M (model 315601) blackWALDLAUFER US 7M Metallic Leather Mary Jane Low Heel Shoe Weite HNEW SCHOLL ORTHAHEEL COMPOSE WOMENS SUPPORTIVE MARY JANE COMFORT SHOES , Air Force 1 Nike Shoes sneakers Size 6 WomensSkechers Smitten Go Walk Lite Women's Blue Slip Loafers Flats US 10 Shoes C046 , Ralph Lauren Sneakers High Top US4 Eur35 Purple Velvet UpperWomen's knitting shoes Mesh Platform Shake Casual Fitness Sport Shoes AthleticIsotoner A9B926 Black Genuine Suede Tommy Closed Back Sherpa Lined Slippers , Womens Size 6.5 KEDS Neon Yellow Green Canvas Oxford Tennis Shoe Style SneakersCobb Hill by New Balance Women's 'Wink' Synthetic Sandals Shoe Black Silver 9 MWomens Nike Air Winterspike ACG All Trac Running Shoes US 9 TrainersOn Cloud Womens Cloudrunner Red Running Shoes Size 7.5 (367049) , New Balance Barringer 890 v2 Running Shoes Women’s Size 8.5 US Great conditionWOMENS SAUCONY GRID EXCURSION TR8 BLACK BLUE RUNNING SHOES SIZE 10W G799 , Woman's Skechers SN11860 Air-Cooled Memory Foam D'Lites Size 6.5 , Womens 8.5 M JBU jambu sport sider barefoot water shoes slip-on loafers tan flatWomen's Nike Air Presto Ultra Luxuriant In Design Athletic Shoes , New Balance 696 Women's Size 7 US B Medium WL696SUA NWOBNautica Long Bay Slip On Fashion Sneakers, White, 8.5 US / 39 EU , VANS Sk8 Hi Reissue (Denim C&L) Periscope/Dachshund MEN'S 7 WOMEN'S 8.5Newton Women's Lady Isaac S - Pink/Lime (W011813) , Hush Puppies Achieve Womens Size 7 N White Leather Walking Shoes , Sneakers and Athletic G by GUESS Malden Oat Embossed LogoWomen's Brooks Launch 2 Running Shoe Sneaker Athletic Cross Train Purple sz 9ASICS Gel contend 3 Sneakers Sz 9 Running Shoes Aqua Blue Neon Orange Silver
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."